1. Field of the Invention
The present invention relates to an image-forming device such as a laser printer, and a developer cartridge detachably mounted in the image-forming device.
2. Description of the Related Art
In conventional laser printers, developer cartridges accommodating toner are detachably mounted therein. This type of laser printer is provided with new product detecting means for detecting whether the developer cartridge mounted in the laser printer is a new product and for determining the life of the developer cartridge from the point that the new product was detected.
For example, Japanese unexamined patent application publication No. 2000-221781 proposes a developer cartridge that is provided with a sector gear having a recessed part and a protruding part. When the new developer cartridge is mounted in the body of an electrophotographic image-forming device, the protruding part formed on the sector gear is inserted into a new product side sensor, turning the new product side sensor on. After the developer cartridge has been mounted in the body of the image-forming device, an idler gear is driven to rotate. When the idler gear begins to rotate, the sector gear also rotates, moving the protruding part from the new product side sensor to an old product side sensor. The protruding part is inserted into the old product side sensor, turning the old product side sensor on. At the same time, the idler gear arrives at the recessed part of the sector gear, and the sector gear stops rotating.
However, in the new product detecting means described in Japanese unexamined patent application publication No. 2000-221781, both a new product side sensor and an old product side sensor are essential because the protruding part is inserted either into the new product sensor for detecting a new product or the old product sensor for detecting an old product. Accordingly, this structure increases the cost and complexity of the developing device.
Further, some users have requested the freedom to select an optimum developer cartridge from a plurality of developer cartridges in different price ranges corresponding to the amount of toner accommodated therein with consideration for cost and frequency of use.
To meet this demand, developer cartridges accommodating different amounts of toner must be provided. However, since the toner accommodated in these developer cartridges has different agitation properties based on the amount of toner, rates of degradation of the toner is also different based on the amount of toner.
Under these circumstances, it is not sufficient merely to detect whether the developer cartridge is a new product since the life of the developer cartridge from this point of detection may differ according to the amount toner accommodated therein. Accordingly, the life of the developer cartridge cannot be accurately determined. As a result, a developer cartridge accommodating a small amount of toner may actually reach the end of its life before such a determination is made, resulting in a decline in image quality.